There are significantly improved required peak rates in a Long Term Evolution-Advanced (LTE-A) system up to 1 Gbps in the downlink and 500 Mbps in the uplink as compared with the LTE system.
Thus the technology of Carrier Aggregation (CA) has been introduced so that a plurality of consecutive or inconsecutive carriers served by the same evolved Node B (eNB) are aggregated together to serve a User Equipment (UE) concurrently, and FIG. 1 illustrates a schematic diagram of an application scheme of the CA technology in the prior art.
These carriers aggregated together are also referred to as Component Carriers (CCs). In order to ensure compatibility with UEs in the LTE system, the bandwidth of each carrier is up to 20 MHz.
In another aspect, Uplink Control Information (UCI) will be described as follows:
The UCI includes Acknowledgement/Non-Acknowledgement (ACK/NACK) information, periodic Channel State Information (CSI) and Scheduling Request (SR) information.
The periodic CSI particularly includes Rank Indicator (RI) information, Channel Quality Indicator (CQI) information, Precoding Matrix Indicator (PMI) information and Precoder Type Indication (PTI) information.
In the LTE-A CA system, Physical Uplink Control Channel (PUCCH) format 3 is defined for transmission of multi-bit ACK/NACK information of a plurality of aggregated carriers. The maximum transmission capacity of the PUCCH format 3 is 22 bits and can support jointly encoded transmission of at most 20 bits of ACK/NACK and a 1-bit SR.
In the Rel-10 system, concurrent transmission of ACK/NACK information of a plurality of carriers and periodic CSI over a PUCCH is not supported, and if there are both ACK/NACK of a plurality of carriers and periodic CSI in a current subframe, then only the ACK/NACK is transmitted over the PUCCH whereas the CSI is dropped.
For a UE transmitting ACK/NACK using PUCCH format 3, only when support for concurrent transmission of ACK/NACK and CSI in a subframe is configured and a single downlink subframe is received only on a Primary Component Carrier (PCC), concurrent transmission of ACK/NACK of the received downlink subframe and periodic CSI of one carrier using PUCCH format 2/2a/2b is supported. If there are a plurality of carriers for which CSI needs to be fed back concurrently in a current subframe, then CSI of one carrier with high CSI reporting type priority is selected to be reported according to predefined CSI reporting type priorities, where the highest priority reporting types are the types 3, 5, 6 and 2a, the second highest priority reporting types are the types 2, 2b, 2c and 4, and the lowest priority reporting types are the types 1 and 1a, and CSI report contents and bits corresponding to each CSI reporting type in different reporting modes are as depicted in Table 1, and only one reporting type of each activated carrier of the UE is reported in one uplink subframe according to currently configured reporting types and a particular state. If there are a plurality of carriers with the same reporting type priority, then CSI of the carrier with the lowest index is further selected to be reported according to indexes of the carriers.
Table 1 depicts CSI report contents and bits corresponding to CSI reporting types in different reporting modes.
Reporting ModesReportingReportMode 1-1Mode 2-1Mode 1-0Mode 2-0TypecontentsMode state(bits/BP)(bits/BP)(bits/BP)(bits/BP)1Sub-bandRI = 1NA4 + LNA4 + LCQIRI > 1NA7 + LNA4 + L 1aSub-band8 antenna ports RI = 1NA8 + LNANACQI/8 antenna ports 1 < RI < 5NA9 + LNANAsecond PMI8 antenna ports RI > 4NA7 + LNANA2Wideband2 antenna ports RI = 166NANACQI/PMI4 antenna ports RI = 188NANA2 antenna ports RI > 188NANA4 antenna ports RI > 11111NANA 2aWideband8 antenna ports RI < 3NA4NANAfirst PMI8 antenna ports 2 < RI < 8NA2NANA8 antenna ports RI = 8NA0NANA 2bWideband8 antenna ports RI = 188NANACQI/8 antenna ports 1 < RI < 41111NANAsecond PMI8 antenna ports RI = 41010NANA8 antenna ports RI > 477NANA 2cWideband8 antenna ports RI = 18NANANACQI/first8 antenna ports 1 < RI ≦ 411NANANAPMI/8 antenna ports 4 < RI ≦ 79NANANAsecond PMI8 antenna ports RI = 87NANANA3RI2/4 antenna ports, 2-layer1111spatial multiplexing8 antenna ports, 2-layer1NANANAspatial multiplexing4 antenna ports, 4-layer2222spatial multiplexing8 antenna ports, 4-layer2NANANAspatial multiplexing8-layer spatial multiplexing3NANANA4WidebandRI = 1 or RI > 1NANA44CQI5RI/first PMI8 antenna ports, 2-layer4NANANAspatial multiplexing8 antenna ports, 4 and58-layer spatial multiplexing6RI/PTI8 antenna ports, 2-layerNA2NANAspatial multiplexing8 antenna ports, 4-layerNA3NANAspatial multiplexing8 antenna ports, 8-layerNA4NANAspatial multiplexing
For Table 1, it shall be noted that:
The bits/BP represents a number of report bits per Bandwidth Part; the CQI/PMI is categorized as a wideband CQI/PMI and a sub-band CQI/PMI; the antenna ports represent antenna ports; the layer represents a transmission layer; the spatial multiplexing represents spatial multiplexing; the NA indicates that the reporting type is not supported in a corresponding reporting mode; and L represents label of a selected sub-band in at most 2 bits.
In the LTE-A Rel-11 CA system, enhanced transmission of UCI has been investigated, and in order to avoid an influence upon downlink scheduling of an eNB caused by excessively CSI dropping, concurrent transmission of ACK/NACK of multiple carriers and periodic CSI of one carrier using PUCCH format 3 is supported, and when there is an SR, concurrent transmission thereof with a 1-bit SR can be further supported.